It’s no secret that the 21st century has brought with it a myriad of societal, cultural, and technological revolutions. The crown jewel of changes, however, has been the growth of our insatiable appetite for information – and it shows no signs of slowing down. The question arises, how do we keep up?
Let’s start with the story so far.
The 1980s saw the beginning of the commercial use of computers, which brought the semiconductor industry to life. The semiconductor industry has continually created ICs (integrated circuits) that developed computer memory into what it is today. However, the last decade has started to test the limits of this approach.
The power of these chips has largely come from the evolution of the fabrication processes behind them. However, the integrative process that sustained the industry for the last 50 years has its limitations, especially when using electronic systems. When compared to photons, electrons are relatively sluggish since they have mass. They also interact with each other and the wiring through which they travel. However, the core problem lies in the charge-discharge cycle [1] required when transferring data between two points in a conventional electronic system. Even the most microscopic of systems require that wires are charged and discharged during any transmission, which needs both energy (causing power dissipation) and time.
As we approach the theoretical limits of electronic systems, we start to hit a “power wall” [2] for all the reasons listed above. Every further boost in bandwidth comes with an inordinate increase in power requirements and data losses to an unsustainable extent. Cue integrated photonics.
Any basic communications and information processing system have 3 high-level stages: the generation, transmission, and detection of a signal. Traditional photonics systems complete these steps across discrete components with the physical distance between them. Fiber-optic data transmission is a key example of this. However, the last 5-10 years have seen the emergence of an alternative approach: integrated photonics.
Integrated photonics, essentially, tries to replace electrons in ICs with photons. Fabricating photonic components onto a single piece of silicon has been the main challenge, though. However, Key breakthroughs in the last few years have shown that the techniques (CMOS) used for electronic fabrication can be used to create photonic integrated circuits (PICs). This alleviates the cost of having to switch from basic manufacturing equipment and paves the way for a new generation of connectivity products.
Integrated photonics is creating innovation in a long, expanding list of applications. As mentioned earlier, the key long-term application is in computing as a new generation of integrated circuits for the semiconductor industry.
One of the first uses that come to mind is in biosensing. The traditional approach the healthcare industry uses is to only treat patients who are seriously ill enough that they lack the resources to help themselves. However, the high cost of this approach has made prevention a higher priority. Implementing this requires monitoring and frequent testing, which is only logistically possible when it is decentralized [5] and away from the hospital. This drawback kickstarted the development of “lab-on-a-chip” technologies [3] that sidestep the hassle of large-scale, drawn-out laboratory testing. These redundancies came into full view during the pandemic, highlighting how cumbersome testing is. Light has been used in hospital-grade devices because its effects (reflection, scattering, refraction) change in a predictable manner during its interaction with given body tissues and fluids. Integrated photonics has the potential to dramatically reduce both the cost and size of these devices and, thus, improve point-of-care testing and perhaps the early diagnosis of common diseases.
Integrated photonics is also set to play a role in the automotive industry. Navigation is a key challenge for the development of autonomous vehicles. LIDAR (Light Detection and Ranging) is one of the most promising approaches used, under its direct detection of velocity and range with high resolution [4]. However, these systems still use discrete photonic components which increase their cost and physical footprint beyond commercial viability. Additionally, later generations of these navigation systems will require processing speed at levels that electronic chips cannot meet. The use of integrated photonics offers both higher production output and faster processing that will bring down cost and boost processing speed perhaps to the point of commercial feasibility.
The introduction of IoT-connected (Internet of Things) devices will place unprecedented demands on telecommunication speeds when widely implemented. The speed that light-based systems bring to the table could boost the transmission capacities of current communication systems. In addition to making faster transceivers, integrated photonics could play a key role in data centers [5]. It may allow an architecture that uses rapid photonic switching and networking to reduce energy consumption and create high degrees of flexibility when routing data through to optimize facility usage.
The final use of integrated photonics we will discuss is in high-performance computing (HPC). A major restriction in HPC is the relative communication delays between components. Memory that is stored near the CPU (cache memory), is far faster because of the time associated with the transmission through copper wiring. What if we removed the wiring? The proximity of the memory to the CPU would no longer be a factor in transmission speed. Photonic systems allow this and effectively allow a unified memory unit with components connected by optical links that all act at almost equal, cache-level speeds. This is just a single application of integrated photonics in HPC. CPU performance, external sensing, and control systems to optimize resource management could all use integrated photonics in a manner that collectively revolutionizes high-performance computing.
The exciting part of disruptive technologies like integrated photonics is the unknown of it all. Will it transform industries and inspire a whole new set of equally disruptive innovations? Will it radically change our way of life? How? Or is it all going to be decades of research and countless lives’ work that amounts to nothing? We’ll just have to wait and see
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